From d235e2c6a5788ec4a6cff15a16f56b38a3876a0d Mon Sep 17 00:00:00 2001 From: Determinant Date: Sun, 28 Jun 2020 14:47:41 -0400 Subject: ... --- rpc/service.go | 285 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 285 insertions(+) create mode 100644 rpc/service.go (limited to 'rpc/service.go') diff --git a/rpc/service.go b/rpc/service.go new file mode 100644 index 0000000..ead6fb6 --- /dev/null +++ b/rpc/service.go @@ -0,0 +1,285 @@ +// Copyright 2019 The go-ethereum Authors +// This file is part of the go-ethereum library. +// +// The go-ethereum library is free software: you can redistribute it and/or modify +// it under the terms of the GNU Lesser General Public License as published by +// the Free Software Foundation, either version 3 of the License, or +// (at your option) any later version. +// +// The go-ethereum library is distributed in the hope that it will be useful, +// but WITHOUT ANY WARRANTY; without even the implied warranty of +// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +// GNU Lesser General Public License for more details. +// +// You should have received a copy of the GNU Lesser General Public License +// along with the go-ethereum library. If not, see . + +package rpc + +import ( + "context" + "errors" + "fmt" + "reflect" + "runtime" + "strings" + "sync" + "unicode" + "unicode/utf8" + + "github.com/ava-labs/go-ethereum/log" +) + +var ( + contextType = reflect.TypeOf((*context.Context)(nil)).Elem() + errorType = reflect.TypeOf((*error)(nil)).Elem() + subscriptionType = reflect.TypeOf(Subscription{}) + stringType = reflect.TypeOf("") +) + +type serviceRegistry struct { + mu sync.Mutex + services map[string]service +} + +// service represents a registered object. +type service struct { + name string // name for service + callbacks map[string]*callback // registered handlers + subscriptions map[string]*callback // available subscriptions/notifications +} + +// callback is a method callback which was registered in the server +type callback struct { + fn reflect.Value // the function + rcvr reflect.Value // receiver object of method, set if fn is method + argTypes []reflect.Type // input argument types + hasCtx bool // method's first argument is a context (not included in argTypes) + errPos int // err return idx, of -1 when method cannot return error + isSubscribe bool // true if this is a subscription callback +} + +func (r *serviceRegistry) registerName(name string, rcvr interface{}) error { + rcvrVal := reflect.ValueOf(rcvr) + if name == "" { + return fmt.Errorf("no service name for type %s", rcvrVal.Type().String()) + } + callbacks := suitableCallbacks(rcvrVal) + if len(callbacks) == 0 { + return fmt.Errorf("service %T doesn't have any suitable methods/subscriptions to expose", rcvr) + } + + r.mu.Lock() + defer r.mu.Unlock() + if r.services == nil { + r.services = make(map[string]service) + } + svc, ok := r.services[name] + if !ok { + svc = service{ + name: name, + callbacks: make(map[string]*callback), + subscriptions: make(map[string]*callback), + } + r.services[name] = svc + } + for name, cb := range callbacks { + if cb.isSubscribe { + svc.subscriptions[name] = cb + } else { + svc.callbacks[name] = cb + } + } + return nil +} + +// callback returns the callback corresponding to the given RPC method name. +func (r *serviceRegistry) callback(method string) *callback { + elem := strings.SplitN(method, serviceMethodSeparator, 2) + if len(elem) != 2 { + return nil + } + r.mu.Lock() + defer r.mu.Unlock() + return r.services[elem[0]].callbacks[elem[1]] +} + +// subscription returns a subscription callback in the given service. +func (r *serviceRegistry) subscription(service, name string) *callback { + r.mu.Lock() + defer r.mu.Unlock() + return r.services[service].subscriptions[name] +} + +// suitableCallbacks iterates over the methods of the given type. It determines if a method +// satisfies the criteria for a RPC callback or a subscription callback and adds it to the +// collection of callbacks. See server documentation for a summary of these criteria. +func suitableCallbacks(receiver reflect.Value) map[string]*callback { + typ := receiver.Type() + callbacks := make(map[string]*callback) + for m := 0; m < typ.NumMethod(); m++ { + method := typ.Method(m) + if method.PkgPath != "" { + continue // method not exported + } + cb := newCallback(receiver, method.Func) + if cb == nil { + continue // function invalid + } + name := formatName(method.Name) + callbacks[name] = cb + } + return callbacks +} + +// newCallback turns fn (a function) into a callback object. It returns nil if the function +// is unsuitable as an RPC callback. +func newCallback(receiver, fn reflect.Value) *callback { + fntype := fn.Type() + c := &callback{fn: fn, rcvr: receiver, errPos: -1, isSubscribe: isPubSub(fntype)} + // Determine parameter types. They must all be exported or builtin types. + c.makeArgTypes() + if !allExportedOrBuiltin(c.argTypes) { + return nil + } + // Verify return types. The function must return at most one error + // and/or one other non-error value. + outs := make([]reflect.Type, fntype.NumOut()) + for i := 0; i < fntype.NumOut(); i++ { + outs[i] = fntype.Out(i) + } + if len(outs) > 2 || !allExportedOrBuiltin(outs) { + return nil + } + // If an error is returned, it must be the last returned value. + switch { + case len(outs) == 1 && isErrorType(outs[0]): + c.errPos = 0 + case len(outs) == 2: + if isErrorType(outs[0]) || !isErrorType(outs[1]) { + return nil + } + c.errPos = 1 + } + return c +} + +// makeArgTypes composes the argTypes list. +func (c *callback) makeArgTypes() { + fntype := c.fn.Type() + // Skip receiver and context.Context parameter (if present). + firstArg := 0 + if c.rcvr.IsValid() { + firstArg++ + } + if fntype.NumIn() > firstArg && fntype.In(firstArg) == contextType { + c.hasCtx = true + firstArg++ + } + // Add all remaining parameters. + c.argTypes = make([]reflect.Type, fntype.NumIn()-firstArg) + for i := firstArg; i < fntype.NumIn(); i++ { + c.argTypes[i-firstArg] = fntype.In(i) + } +} + +// call invokes the callback. +func (c *callback) call(ctx context.Context, method string, args []reflect.Value) (res interface{}, errRes error) { + // Create the argument slice. + fullargs := make([]reflect.Value, 0, 2+len(args)) + if c.rcvr.IsValid() { + fullargs = append(fullargs, c.rcvr) + } + if c.hasCtx { + fullargs = append(fullargs, reflect.ValueOf(ctx)) + } + fullargs = append(fullargs, args...) + + // Catch panic while running the callback. + defer func() { + if err := recover(); err != nil { + const size = 64 << 10 + buf := make([]byte, size) + buf = buf[:runtime.Stack(buf, false)] + log.Error("RPC method " + method + " crashed: " + fmt.Sprintf("%v\n%s", err, buf)) + errRes = errors.New("method handler crashed") + } + }() + // Run the callback. + results := c.fn.Call(fullargs) + if len(results) == 0 { + return nil, nil + } + if c.errPos >= 0 && !results[c.errPos].IsNil() { + // Method has returned non-nil error value. + err := results[c.errPos].Interface().(error) + return reflect.Value{}, err + } + return results[0].Interface(), nil +} + +// Is this an exported - upper case - name? +func isExported(name string) bool { + rune, _ := utf8.DecodeRuneInString(name) + return unicode.IsUpper(rune) +} + +// Are all those types exported or built-in? +func allExportedOrBuiltin(types []reflect.Type) bool { + for _, typ := range types { + for typ.Kind() == reflect.Ptr { + typ = typ.Elem() + } + // PkgPath will be non-empty even for an exported type, + // so we need to check the type name as well. + if !isExported(typ.Name()) && typ.PkgPath() != "" { + return false + } + } + return true +} + +// Is t context.Context or *context.Context? +func isContextType(t reflect.Type) bool { + for t.Kind() == reflect.Ptr { + t = t.Elem() + } + return t == contextType +} + +// Does t satisfy the error interface? +func isErrorType(t reflect.Type) bool { + for t.Kind() == reflect.Ptr { + t = t.Elem() + } + return t.Implements(errorType) +} + +// Is t Subscription or *Subscription? +func isSubscriptionType(t reflect.Type) bool { + for t.Kind() == reflect.Ptr { + t = t.Elem() + } + return t == subscriptionType +} + +// isPubSub tests whether the given method has as as first argument a context.Context and +// returns the pair (Subscription, error). +func isPubSub(methodType reflect.Type) bool { + // numIn(0) is the receiver type + if methodType.NumIn() < 2 || methodType.NumOut() != 2 { + return false + } + return isContextType(methodType.In(1)) && + isSubscriptionType(methodType.Out(0)) && + isErrorType(methodType.Out(1)) +} + +// formatName converts to first character of name to lowercase. +func formatName(name string) string { + ret := []rune(name) + if len(ret) > 0 { + ret[0] = unicode.ToLower(ret[0]) + } + return string(ret) +} -- cgit v1.2.3